London Calling: FDSOI clocks at 3GHz

ST has obtained application processor engines that can operate at clock frequencies in excess of 3GHz providing a boost to the performance claims for the process.

STMicroelectronics is keeping the pot boiling for its fully-depleted silicon-on-insulator (FDSOI) manufacturing process. The latest piece of information shared is that the 28-nm version of the process has produced application processor "engines" capable of being operated at clock frequencies in excess of 3GHz.

ST has not mde clear what the difference between an engine and a processor is, or what extremes of operating temperature were tolerated to achieve the 3-GHz.

For reference the NovaThor L8580 LTE-capable application processor from ST-Ericsson has been benchmarked at operating at
up to 2.5-GHz clock frequency at peak performance, but also capable of
operating down at 0.6-V to conserve power. So it might be reasonable to infer that ST is saying the L8580 and processors like it could be pushed to beyond 3-GHz if the developers so desired.

The FDSOI planar process, which for now remains a minority interest being promoted by ST, is claimed to have advantages over other more mainstream manufacturing process variants, such as bulk planar CMOS and FinFET CMOS in terms of trade-offs between performance, power consumption and manufacturability.

The use of back baising of silicon beneath the oxide insulator theoretically allows additional high-end performance and the SOI process can also produce operational circuits at lower voltages than alternative processes, proponents claim.

ST has previously claimed that at 28-nm, its FDSOI process can provide 30 percent more performance than bulk 28-nm CMOS at the same power consumption, or, alternatively, can provide as much as a 50 percent saving in dynamic power consumption at the same performance. That claim may be increased as the company pushes out the top-end performance.

"As we had anticipated, FDSOI is proving to be fast, simple and cool; we had fully expected to see 3GHz operating speeds, the design approach is very consistent with what we had been doing in bulk CMOS, and, with the benefits of fully depleted channels and back biasing, the low-power requirements are also meeting our expectations," said Jean-Marc Chery, chief technology and manufacturing officer of STMicroelectronics, in a statement.

ST said it has found the porting of libraries and physical IP from 28-nm bulk CMOS to 28-nm FDSOI to be straightforward. The process of then designing digital circuits with conventional CAD tools has been identical to designing for bulk CMOS, the company said.

ST will be demonstrating the FDSOI technology at the Mobile World Congress in Barcelona from Feb. 25 to 28.

SOITEC provides 12nm wafers because they are asked to. It's not that they are limited to 12nm and manufacturers have to take the extra burden of thinning the wafer to the desired thickness. You need a few nm as a part of STI formation (so-called padox) and a few nm for thick oxide devices and HK gate pre-clean. All these steps are precise oxidation steps that have been used in in the industry for many years to form the gate oxide (which has been by far the most uniform process step in ic manufacturing).

IBM invented PDSOI, FDSOI, and E (extremely)T (thin) SOI technologies over twenty years of time period. PDSOI was very successful products. IBM and its SOI Consortium have spent enormous resources and efforts for volume manufacture of FDSOI and ETSOI including UTBB, but have not been successful. No FDSOI is manufactured at any node even today or the 22nm era. The major reason is for the 28 node a 7nm and for 22nm node 5.5nm extremely thin channel ETSOI are required to suppress the transistor leakage current or short channel effects. However, such ultra-thin 7nm and 5.5 nm ETSOI canít be manufactured by Soitec. What Soitec can deliver today is 28nm SOI wafers with minimum channel thickness of 12nm and 25nm buried oxide. Therefore, STMís repeated claims to have advantages over planar bulk CMOS and FinFETs in performance, power consumption and manufacturability are not justified because the 28nm planar bulk is in high volume manufacturing over 3 years and Intelís FinFETs are also in high volume manufacturing for almost 2 years, but STMís FDSOI is not manufactured yet and not likely.
STMís 28nm wafer process sounds like etching back 5nm silicon from the 12nm silicon film to obtain a final 7nm. My question is such an extremely thin 5nm silicon can be etched back to obtain a final 7nm uniformly and reliably across the 300mm wafer in volume manufacturing. It sounds like a test chip or test wafer process. The published 7nm and 6nm data is test chip or test wafer data. STM claims it is qualified for production.